Loudspeaker, manufacturing method thereof, and mobile telephone using the same

ABSTRACT

A loudspeaker used mainly for mobile communication equipment such as a mobile telephone and having two loudspeaker parts provided in one frame is provided. In the loudspeaker, a yoke has a groove portion and a second voice coil disposed in this groove portion drives a second diaphragm. Since the groove portion functioning as a magnetic gap is formed by processing the yoke, variation in the magnetic gap, which conventionally occurred at the time of incorporation, is eliminated and accuracy is improved, thus stabilizing the sound pressure frequency property.

TECHNICAL FIELD

The present invention relates to a loudspeaker used for mobilecommunication such as a mobile telephone, a method for manufacturing thesame and a mobile telephone using the same.

BACKGROUND ART

Although a mobile telephone is small in size, it has a loudspeaker forringing or amplifying the sound in addition to a receiving loudspeaker.In particular, since there is a limit to miniaturization of small-sizedequipment such as folding type equipment, two loudspeaker parts arebuilt in one frame. FIG. 8 is a sectional view showing a conventionalloudspeaker of this kind.

Hollow cylindrical frame 1 formed by resin molding has convex part 1Aprotruding inwardly all around a center part of an inner circumferentialsurface. Ring-shaped first magnet 2 is bonded to convex portion 1A atits outer circumferential side surface. Cup-shaped yoke 3 made of amagnetic material such as iron is bonded to first magnet 2 at its lowersurface of an outer circumference. Columnar second magnet 4 is bonded toa center part of yoke 3. Annular first plate 6 is bonded to a lowersurface of first magnet 2, and second plate 5 is bonded to an uppersurface of second magnet 4. Annular first magnetic gap 7 is providedbetween an inner circumference of first plate 6 and the outercircumference of the center part of yoke 3. Annular second magnetic gap8 is formed between an outer circumference of second plate 5 and aninner circumference of the center part of yoke 3.

In the above-mentioned configuration, first magnet 2, yoke 3, firstmagnetic gap 7 and first plate 6 form a first magnetic circuit.Furthermore, second magnet 4, second plate 5, second magnetic gap 8 andyoke 3 form a second magnetic circuit.

First diaphragm 9 is placed at a lower side opening of frame 1. Annularfirst voice coil 10 is bonded to first diaphragm 9 at its lower end andlocated in first magnetic gap 7 at another end. First protector 10A hasa plurality of holes for releasing sound and is bonded to outercircumferences of frame 1 and first diaphragm 9 such that it coversfirst diaphragm 9. Second diaphragm 11 is bonded to an upper sideopening of frame 1. Annular second voice coil 12 is bonded to seconddiaphragm 11 at its upper end and located in second magnetic gap 8 atanother end. Second protector 13 has a plurality of holes for releasingsound and is bonded to outer circumferences of frame 1 and seconddiaphragm 11 such that it covers second diaphragm 11. Such a loudspeakeris disclosed in, for example, Japanese Patent Unexamined Publication No.2003-111194.

When a loudspeaker having the above-mentioned configuration includingtwo loudspeaker parts is used for, for example, a mobile telephone, oneloudspeaker part is used as a receiver for receiving and another is usedfor a loudspeaker for notifying incoming of call or a loudspeaker.Furthermore, the loudspeaker can be used as a small-sized stereoloudspeaker by inputting LR signals, respectively.

However, since in the loudspeaker having such a configuration, twomagnetic circuits are built in, it is difficult to reduce weight. Also,the configuration is complicated, resulting in increase in the number ofcomponents and the man-hour required for assembly. Accordingly, the costis high. Note here that although there is a loudspeaker having twodiaphragms in one magnetic circuit, variation is likely to occur in asound pressure frequency property. Therefore, strict assembly accuracyis required, and assembly itself is complex

SUMMARY OF THE INVENTION

A loudspeaker of the present invention is a composite type loudspeakerfor driving two diaphragms in one magnetic circuit. The loudspeakerincludes a hollow frame, a magnet, a yoke, a plate, a first voice coil,a first diaphragm, a second voice coil and a second diaphragm. The frameincludes a first opening and a second opening facing the first opening.The magnet is provided inside the frame, and has a first pole and asecond pole facing the first opening and the second opening,respectively. The plate made of a magnetic material is provided incontact with the first pole of the magnet. The yoke made of a magneticmaterial is provided in contact with the second pole of the magnet,forms magnetic flux flow between the first pole and the second pole andhas a groove portion on a surface facing the second opening. The firstvoice coil has a first end located in a magnetic gap provided betweenthe yoke and the plate. The first diaphragm is bonded to a second end ofthe first voice coil and bonded to the first opening of the frame at itsouter periphery. The second voice coil has a first end located in thegroove portion. The second diaphragm is bonded to a second end of thesecond voice coil and bonded to the second opening of the frame at itsouter periphery.

In a method for manufacturing a loudspeaker of the present invention, ayoke is provided with a groove portion.

A mobile telephone of the present invention uses a second loudspeakerpart including the second diaphragm of the above-mentioned loudspeakeras a receiver for releasing sound from another end of the telephone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view showing a loudspeaker according to anembodiment of the present invention.

FIGS. 2 and 3 are side sectional views showing modifications of theloudspeaker shown in FIG. 1.

FIG. 4 is a side sectional view showing another loudspeaker according toan embodiment of the present invention.

FIG. 5 is a top sectional view showing a mobile telephone according toan embodiment of the present invention.

FIG. 6 is a top front view showing the mobile telephone shown in FIG. 5.

FIG. 7 is a block diagram showing a configuration of a mobile telephoneaccording to an embodiment of the present invention.

FIG. 8 is a sectional view showing a conventional loudspeaker.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1 is a sectional view showing a loudspeaker according to anembodiment of the present invention. Hollow cylindrical frame 21 isformed by resin molding. Yoke 22 has a U-shaped cross section and ismade of iron that is a magnetic metal. An outer wall portion of yoke 22is integrated with frame 21 by insert molding and supported by an innerwall of frame 21. Columnar magnet 23 having a first pole and a secondpole (north pole and south pole) at lower and upper sides is providedinside yoke 22 with the second pole attached to a center of a topsurface of yoke 22. Plate 24 is also made of a magnetic material and isattached to the lower surface, that is, the first pole of magnet 23.Both poles of magnet 23 face first opening 21A and second opening 21B offrame 21, respectively. Between the outer wall of yoke 22 and plate 24,magnetic gap 25 is formed. First diaphragm 26 is attached to firstopening 21A of frame 21 at its outer periphery. To the end part, asecond end of first voice coil 26A is attached, while a first endthereof is located in magnetic gap 25. Yoke 22 forms magnetic flux flowbetween the both poles of magnet 23.

Groove portion 27 is provided on a surface facing second opening 21B ofyoke 22, and second diaphragm 28 is attached to second opening 21Bfacing first opening 21A of frame 21 at its outer periphery. To an endof second diaphragm 28, a second end of second voice coil 29 isattached, while first end of second voice coil 29 is located in grooveportion 27. Note here that groove portion 27 has a width and a depthappropriately set to generate magnetic saturation by suitably narrowinga magnetic path of yoke 22 that forms a magnetic circuit, and tofunction as a second magnetic gap. Accordingly, magnetic flux leakinginto groove portion 27 that is the second magnetic gap is increased, andan output of sound pressure of the loudspeaker is increased. In theabove-mentioned configuration, magnet 23, plate 24, magnetic gap 25,voice coil 26A, yoke 22, and diaphragm 26 form a first loudspeaker part.Furthermore, magnet 23, plate 24, groove portion 27, voice coil 29, yoke22, and diaphragm 28 form a second loudspeaker part.

First protector 30 provided with a plurality of holes 30A for releasingsound and second protector 31 provided with center hole 31A arerespectively attached to first and second openings 21A and 21B of frame21 such that they cover diaphragm 26 and 28, respectively. Terminalboards 32 are provided at four portions of frame 21 and electricallyconnected (not shown) to both ends of first voice coil 26A and secondvoice coil 29, respectively.

Ring-shaped groove portion 27 can be formed extremely easily by castingat the same time yoke 22 is formed. Furthermore, groove portion 27 canbe extremely easily formed by forging of sheet-like or hoop-shaped ironmaterial before, after or when yoke 22 is formed. In this way, sincegroove portion 27 is formed by casting or forging and used as the secondmagnetic gap, the second magnetic gap can be finished to have a certainshape and size with high accuracy when yoke 22 is formed. Therefore,when the loudspeaker is incorporated, no error in incorporating themagnetic gap occurs.

Furthermore, since yoke 22 and frame 21 are integrated with each other,eccentric error of magnetic gap 25 with respect to frame 21 when theloudspeaker is incorporated is suppressed. Furthermore, incorporatingerror in the location relation between second voice coil 29 and grooveportion 27 that is the second magnetic gap is also suppressed.Accordingly, the sound pressure frequency property of the loudspeaker isstabilized.

In the loudspeaker configured as mentioned above, groove portion 27provided in yoke 22 functions as the second magnetic gap into whichsecond voice coil 29 is inserted, and two loudspeakers are included.

FIG. 2 is a side sectional view showing a modification of theabove-mentioned configuration. This configuration is different from theconfiguration shown in FIG. 1 in groove portion 27A. This configurationincludes standing wall (hereinafter, which is referred to as “wall”) 27Bformed by extending both side walls of groove portion 27A upwardly. Byproviding wall 27B, the depth of groove portion 27A is increased, aswell as leakage flux is more concentrated to improve the magneticefficiency, and the output of sound pressure of the loudspeaker isincreased to improve the sound pressure frequency property.

Note here that in FIG. 2, wall 27B is provided on both sides of grooveportion 27A, but it may be provided on only one side if necessary.

Furthermore, when yoke 22 is formed by casting, wall 27B can be formedextremely easily by using a casting mold, and when yoke 22 is formed byforging, wall 27B can be formed extremely easily as a buildup portionwhen groove portion 27A is formed at the time of forging.

FIG. 3 is also a side sectional view showing a modification of theconfiguration shown in FIG. 1. This configuration is different from theconfiguration shown in FIG. 1 in that instead of protector 31, port 33is provided. With port 33, it is possible to release sound from acertain position of equipment into which this loudspeaker isincorporated.

Then, another configuration of the present invention is described. FIG.4 is a side sectional view showing a loudspeaker having anotherconfiguration according to an embodiment of the present invention. FIGS.1 to 3 show configurations of an internal magnetic type loudspeakerhaving columnar magnet 23 in a center part thereof Meanwhile, thisconfiguration shows an external magnetic type loudspeaker usingring-shaped magnet 43.

Frame 41 made of resin has first and second openings 41A and 41B atlower and upper ends and is formed as a hollow frame. Ring-shaped plate42 is made of a magnetic material and integrated with frame 41 by insertmolding. Ring-shaped magnet 43 is attached to plate 42 at its firstpole. Both plate 42 and magnet 43 are provided inside frame 41. Bothpoles of magnet 43 face first opening 41A and second opening 41B offrame 41, respectively. Yoke 44 made of a magnetic material is attachedto a second pole of magnet 43 and has center pole 44A located in athrough hole in a center portion of ring-shaped magnet 43 and plate 42.Yoke 44 forms magnetic flux flow between the first pole and the secondpole of magnet 43.

First diaphragm 45 is attached at its outer circumference such that itcovers first opening 41A. A first end of first voice coil 47 is locatedin magnetic gap 46 between center pole 44A and an inner circumference ofplate 42, and a second end thereof is attached to first diaphragm 45.Second diaphragm 48 is attached at its outer circumference such that itcovers the second opening 41B. A first end of second voice coil 49 islocated in groove portion 44B provided in yoke 44 in an annular shape,and a second end thereof is attached to second diaphragm 48. Protectors50 and 51 are attached to first and second openings 41A and 41B suchthat they cover diaphragms 45 and 48, respectively.

In the configuration, magnet 43, plate 42, magnetic gap 46, voice coil47, yoke 44 and diaphragm 45 form a first loudspeaker part. Furthermore,plate 42, magnet 43, groove portion 44B, voice coil 49, yoke 44 anddiaphragm 49 form a second loudspeaker part.

Note here that groove portion 44B can be formed by casting or forgingwhen yoke 44 is formed. As in FIG. 2, groove portion 44B may be providedwith a standing wall.

In the loudspeaker formed as mentioned above, groove portion 44Bprovided in yoke 44 functions as a second magnetic gap for the secondloudspeaker part, and second voice coil 49 is inserted therein.Therefore, when yoke 44 is formed, the magnetic gap can be finished tohave a certain shape and size with high accuracy. Accordingly, when theloudspeaker is incorporated, no error in incorporating the magnetic gapoccurs.

Furthermore, in this configuration, plate 42 is integrated with frame 41by insert molding. Besides, an outer wall portion of yoke 44 may beintegrated with frame 41 by insert molding. In this case, the relationbetween frame 41 and groove portion 44B provided in yoke 44 isdetermined by accuracy of a mold. Therefore, the location accuracy ofthe magnetic gap is more improved and the quality of the loudspeaker isstabilized.

Note here that for yokes 22 and 44 and plates 24 and 42, a magneticmaterial having high magnetic permeability and low coercive force isused. For example, iron is preferably used. Furthermore, for magnets 23and 43, a magnet material having a large energy product is used. Ferritemagnets, samarium-cobalt magnets, neodymium base magnets, and the likeare preferred. Neodymium base magnets are preferably used because theyhave a high energy product and are suitable for achieving small size andlight weight. If necessary, magnetic materials and magnet materials maybe subjected to an anti-rust treatment.

Frames 21 and 41 are formed by using a resin material. As the resinmaterial, thermoplastic resin that does not need hardening treatment ispreferred. For example, ABS, PBT, etc. are used. If heat resistanceproperty is required, it is more preferable to use thermoplastic resinhaving a glass-transition temperature of 100° C. or more. An examplethereof may include polyamide (PA) that is nylon resin containing glass,which has high heat resistance property and high rigidity. Furthermore,in order to integrate resin material with a different kind of materialsuch as metal, a resin material is required to have an excellentfluidity inside a mold. In order to improve fluidity, various additivesmay be used.

Next, example of mounting the above-described loudspeaker is describedwith reference to FIGS. 5 to 7. FIG. 5 is a sectional view of a mobiletelephone seen from the upper side. FIG. 6 is a front view showing onlya display part at the upper side of the mobile telephone shown in FIG.5. FIG. 7 is a block diagram showing a configuration of the mobiletelephone shown in FIG. 5.

When a call is originated, input part 73 receives a telephone numberthat is information about destination of the call from a user or anoriginating operation based on search for an installed telephonedirectory. Control part 72 transmits radio wave including an originatingsignal from transmitter-receiver 71 to the outside by using antenna 63based on the signal from input part 73. When another end gets anincoming call answers, a communication line is connected. Microphone 74inputs a sound from a user and transmits it to control part 72. Controlpart 72 transmits a signal including sound data fromtransmitter-receiver 71 to the outside by using antenna 63. Furthermore,a signal including sound data of the other end, which are received bytransmitter-receiver 71, is output from second loudspeaker part 77 as asound by control part 72. Display part 75 displays a telephone numberinput from input part 73 by a user or search content of telephonedirectory.

When a call is incoming, transmitter-receiver 71 that receives incomingsignal via antenna 63 transmits the signal to control part 72. Controlpart 72 releases ringtone by first diaphragm 26 of first loudspeakerpart 76. At the same time, incoming number etc. may be displayed ondisplay part 75. Input part 73 receives incoming operation by a user andcontrol part 72 transmits a signal of incoming operation fromtransmitter-receiver 71. Thus, the communication line is connected. Notehere that in a case where transmitter-receiver 71 transmits/receives adigital signal, control part 72 functions also as an encoder and adecoder.

In mobile telephone 60 in which loudspeaker 61 shown in FIG. 1 isincorporated, second diaphragm 28 of second loudspeaker part 77 isprovided at the side of display surface (receiving surface) 62. Withsuch a configuration, second diaphragm 28 is used as a receivingloudspeaker that does not require a large sound pressure output as aloudspeaker using leakage flux in groove portion 27. Furthermore, inloudspeaker 61 having this configuration, as mentioned above, locationaccuracy of the magnetic gap is improved. Therefore, incorporating erroris suppressed, and variation in sound pressure output is suppressed.Equipment having small variation, for listener, in quality of soundpressure output by the mounted loudspeaker is provided. Furthermore, forexample, the reduction of magnets to be used contributes to lighteningthe weight of the equipment. Instead of the loudspeaker shown in FIG. 1,loudspeakers shown in FIGS. 2 and 4 may be used. In a case where theloudspeaker shown in FIG. 4 is used, second diaphragm 48 is provided atthe side of display surface 62.

Note here that this embodiment is described assuming that a loudspeakerhas a columnar shape. In addition to this, in accordance with thenecessity of mounted equipment etc., a loudspeaker may be formed to havean appearance of a rectangular parallelepiped, or an oval, or anelliptical shape. An inside magnetic circuit may be formed in an oval oran elliptical shape other than a circular shape if necessary.Furthermore, the groove portion is not limited to a circular shape andit may be changed to an oval, or an elliptical, a racetrack shape, etc.in accordance with the shape of the magnetic circuit.

INDUSTRIAL APPLICABILITY

In the loudspeaker of the present invention, a groove portion providedin a yoke is used as a magnetic gap. Consequently, incorporating erroroccurring when a loudspeaker is incorporated is suppressed and variationis eliminated, and thus a loudspeaker with stable quality can beachieved.

1. A loudspeaker, comprising: a hollow frame provided with a firstopening and a second opening facing the first opening; a magnet providedinside the frame and having a first pole and a second pole facing thefirst opening and the second opening, respectively; a plate made of amagnetic material, which is provided in contact with the first pole ofthe magnet; a yoke made of a magnetic material, which is provided incontact with the second pole of the magnet, forms magnetic flux flowbetween the first pole and the second pole and has a groove portion on asurface facing the second opening; a first voice coil having a first endlocated in a magnetic gap provided between the plate and the yoke, afirst diaphragm bonded to a second end of the first voice coil andbonded to the first opening of the frame at its outer periphery; asecond voice coil having a first end located in the groove portion; anda second diaphragm bonded to a second end of the second voice coil andbonded to the second opening of the frame at its outer periphery.
 2. Theloudspeaker according to claim 1, wherein the yoke has a U-shaped crosssection and has an outer wall portion supported by an inner wall of theframe, the magnet is provided inside the yoke, and the magnetic gap isprovided between the outer wall portion of the yoke and the plate. 3.The loudspeaker according to claim 1, wherein the magnet and the plateare provided with a through hole in a center part thereof, the yoke hasa center pole located in the through hole of the magnet and the plate,and the magnetic gap is provided between the center pole of the yoke andthe plate.
 4. The loudspeaker according to claim 1, wherein the grooveportion has a width and a depth to allow a magnetic pathway of amagnetic circuit, which is formed of the magnet, the yoke, the magneticgap and the plate, to be magnetically saturated at a location of thegroove portion.
 5. The loudspeaker according to claim 1, wherein theyoke has a standing wall provided at at least one side of the both sidesof the grove.
 6. The loudspeaker according to claim 1, wherein the frameand the yoke are integrated with each other.
 7. A mobile telephone,comprising: the loudspeaker described in claim 1, a transmitter-receiverfor transmitting/receiving an originating signal, an incoming signal anda signal including sound data to/from an outside; a control partreleasing ringtone from a first diaphragm of the loudspeaker based onthe incoming signal received via the transmitter-receiver, and releasingringtone from a second diaphragm of the loudspeaker based on the signalincluding sound data received via the transmitter-receiver; a microphonefor inputting a sound signal transmitted to the control part; and aninput part for receiving input of information about originating andincoming, and transmitting the information to the control part.
 8. Amethod for manufacturing the loudspeaker described in claim 1, themethod comprising steps of: A) providing the yoke with the grooveportion; B) bonding the yoke and the magnet together; C) bonding themagnet and the plate together; D) disposing the first end of the firstvoice coil in the magnetic gap; E) bonding the second end of the firstvoice coil to the first diaphragm; F) disposing the first end of thesecond voice coil in the groove portion; and G) bonding the second endof the second voice coil to the second diaphragm.
 9. The method formanufacturing the loudspeaker according to claim 8, wherein in the stepA, the groove portion is formed by forging at a time when, before orafter the yoke is formed.
 10. The method for manufacturing theloudspeaker according to claim 8, wherein in the step A, the grooveportion is formed by casting when the yoke is formed.
 11. The method formanufacturing the loudspeaker according to claim 8, further comprising astep H) of integrating the frame with the yoke by insert molding anouter wall of the yoke into the frame.